1. Field of the Invention
The present invention relates to a bridge alarm system for indicating to a user whether or not a bridge utilizing the alarm system is safe to cross over. More specifically, the bridge alarm system of the present invention energizes warning lights at at least one end of the bridge if any expansion joint of the bridge exceeds a predetermined width.
2. Description of the Prior Art
U.S. Pat. No. 405,042 issued Jun. 11, 1889 to Moses H. Long discloses a draw bridge signaling device which automatically displays to anyone approaching the bridge a lamp and/or large disc during whenever the bridge is opened.
U.S. Pat. No. 1,213,062 issued Jan. 16, 1917 to Noah O. Baty discloses a bridge signaling device in which electrical contact jaws and blades located on binding posts beneath a bridge are used to complete an electrical circuit. If the electrical circuit is broken because one of the blades separates from one of the jaws, an alarm sounds.
U.S. Pat. No. 2,650,560 issued Sep. 1, 1953 to Joseph B. Bear discloses a device for detecting an unsafe condition of a bridge. A horizontal arm is attached to a crank, which, when rotated, activates a visual alarm. The crank is also attached to a bridge cap so that any relative movement between the cap and the pile will activate the alarm.
U.S. Pat. No. 2,689,341 issued Sep. 14, 1954 to Albert W. Holst discloses a safety device for indicating shifting of a bridge structure. Holst uses an electrical switch comprising a pendulum bar so that if the ring and bar come into contact, indicating a shifting of the bridge, an alarm sounds after a predetermined delay.
U.S. Pat. No. 3,522,790 issued Aug. 4, 1970 to Robert J. Cambre discloses a bridge failure alarm which includes tubular units having flares mounted at the top ends of both. The tubular units are pivotally attached to the spans so as to be located in either an upright or lowered position, wherein weights located at the bottom ends of the tubular units tend to rotate the tubular units to their upright positions. When lowered, the flares on each span face one another and a string is used to attach both flares maintaining the tubular units in their lowered positions until the spans move away from each thereby pulling on the string and igniting the flares when detached from both flares allowing the tubular units to rotate to their upright positions placing the ignited flares is clear view of anyone approaching the bridge.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.